PROJECT SUMMARY Men and women who identify as Black (including African, African American, and Afro- Caribbean) are at increased risk for suboptimal adherence to HIV antiretroviral therapy (ART), and there is a need for improvements and innovation in programs that promote ongoing ART adherence in at-risk populations. Positive affect has been linked to improved health and survival across a number of disease outcomes, and there is growing evidence that it is associated with central components of the HIV care continuum, including improved adherence and retention in care. Positive affect has also been demonstrated to be modifiable and may be a particularly important psychological asset for promoting self-care behavior, in that it is posited to engage several mechanisms of action that have also been linked causally to improved ART adherence, including lower perceived stress, reduced burden of psychological distress, increased resilience, and greater social support. Our team has translated state of the art basic science on methods and processes by which positive affect is most likely to improve adherence in the form of the 3- session APPEAL Program (Affect, Promoting Positive Engagement, and Adherence for Life). We seek to refine the APPEAL protocol to ensure cultural fit with a priority population of Black men and women living with HIV who have challenges with ART adherence, to assess the feasibility and acceptability of the program in the context of a randomized feasibility trial, and to identify whether APPEAL exposure results in changes in mechanisms of action and ART adherence by leveraging measures from the Science of Behavior Change Research Network. This use-inspired project seeks to advance the science of affect and health, by producing a potent and sustainable resource for adherence support that can be readily integrated into clinical care, and which can subsequently be tested in a powered confirmatory trial. This work responds to the 2018 Office of AIDS Research priority of developing behavioral and social science approaches to improving adherence.